Denison Mines Ltd. v. Minister of National Revenue, 74 DTC 6525, [1974] CTC 737, [1976] 1 S.C.R. 245 -- summary under Improvements v. Repairs or Running Expense

A mining company drove passageways into an ore body which were used to extract ore from the balance of the ore body. Although the passageways constituted an enduring benefit, the costs of creating the passageways were less than the revenues from the ore removed in creating the passageways and were deductible therefrom on ordinary principles. The costs accordingly were not capital expenditures.